Square-wave generator



M. T. NADIR SQUARE-WAVE GENERATOR Jan. 16, 1962 Filed July 7, 1959 WIDTH CONTROL 2/ l9 OPPOSITE MOVEMENT l I2 I 29 32 CATHODE D c THYRATRON FOLLOWER I 26 I l 33 I Dc THYRATRON II 524 I 3 34 I ,1 1 Flg. DIFFERENTIATOR I 23 I 22 II I L START CONTROL OPPOSITE MOVEMENT Fig 2 38 DIFFERENTIATOR INVENTOR. MARK r )VAQ/l? 3,191.7,537 SQUARE-WAVE GENERATOR Mark T. Nadir, Burnout, NJ assignor, by mesne assignments, to the United States ct America as represented by the Secretary of the Navy Filed July 7, 1959, Ser. No. 825,617 4 Claims. (Cl. 315230) This invention relates to a variable square wave generator and more particularly to a square wave generator in which the start time and width time are controllable.

According to the invention a power supply having both a positive and negative terminal both of which are variable in voltage is applied across a voltage divider network. A portion of this supply voltage i.e. two voltages, one of which is slightly more positive than the other, are applied across the igniting element of two gas tubes. Thus, one gas tube igniting element is slightly more positive than the other, both igniting elements being below the necessary firing or ignition potential. A positive-going sawtooth voltage waveform is then superimposed on the DC. potentials to each igniting element. The more positive of the two ignition elements will reach its firing or ignition potential at a time prior to the more negative ignition element. Thus, the first gas tube will fire followed by the firing of the second gas tube a short time later. The output of the second gas tube, being a negative-going voltage at the firing point, is then coupled to an extinguishing element of the first gas tube extinguishing the first gas tube. The saw tooth wave-form is also applied through a differentiator to the extinguishing element of the second gas discharge tube. The second gas discharge tube will then be extinguished on the fast fall or trailing edge of saw tooth wave-form. Both thyratron will then be in a condition to respond to the next s awtooth wave-form. The output of the first thyratron will be a square wave the leading edge of which is the point of firing of the first thyratron and the trailing edge of which is the firing point of the second thyratron, which coincides with the extinguishing time of the first thyratron. Thus by varying the potential of each of the output terminals of the power supply, the leading edge time is controlled, and by varying the portion of power supply voltage applied to the igniting elements of the gas discharge tubes the time of the trailing edge of the output waveform is controlled. The output of the first gas tube is then a rectangular or square waveform which can be shifted in time and varied in duration.

It is thus an object of the present invention to provide a square wave which can be controlled in time and duration.

Another object of the present invention is to produce a square wave which is extremely simple and predictable in operation.

A further object is the production of a variable square wave with an extremely high degree of accuracy.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the foregoing detailed description when considered in connection with the accompanied drawings in which like references will designate like parts throughout the figures thereof and wherein:

FIG. -1 illustrates in block and schematic for a preferred embodiment of the present invention;

FIG. 2 illustrates a portion of FIG. 1 in schematic form, and

FIG. 3 illustrates the waveforms in time relationship 1 as they appear throughout the system.

Referring now to the drawings there is shown in PEG. 1 an input terminal 11 connected to coupling capacitors 3&1753? Patented Jan. 16, 1982 "ice 12 and 13 respectively. The other side of capacitors 12 and 13 are connected to resistors 14 and 16 in series with each other, and resistors 17 and 13 also in series with each other and in parallel with resistors 14 and 16. The capacitor 12 is also connected through variable resistor 19 having slidable contact 21 to the positive side of a power supply. Capacitor 13 is connected through variable resistor 22 having slidable contact 23 to the negative side of the power supply. Resistor 16 has slidable contact 24 which is connected to DC. amplifier 26. Resistor 17 has slidable contact 27 which is connected to D.C. amplifier 28. The output of amplifier 28 is connected to the control grid of thyratron 29. The output of amplifier 26 is connected to the control grid of thyratron 31. The output of thyratron 29 is connected to amplifier 32, the output of which is coupled to output terminals 33. The output of thyratron 31 is connected to the screen grid of thyratron 29. Input terminal 11 is also connected to differentiator 34, the output of which is connected to the screen grid of thyratron 31.

In FIG. 2 there is shown schematically the circuits associated with thyratrons 29 and 31. The output of DC. amplifier 28 is connected to grid 36 of thyratron 29. Resistor 37 is connected between grid 36 and the negative side of the power supply. Resistors 38 and 39 are connected between the negative and positive terminals of the power supply. Cathode 41 is connected to the junction of resistors 38 and 39. Plate 42 is also connected to the input of amplifier 32. The output of DC amplifier 26 is connected to grid 43 of thyratron 31. Resister 44 is connected between grid 43 and the negative terminal of the power supply. Resistors 46 and 47 are connected between the negative and positive terminals of the power supply. Cathode 48 is connected to the junction of resistors 46 and 47. Plate 57 is connected through resistors 49 to the positive side of the power supply. Plate 48 is also connected through resistors 50 and 51 in series to the negative side of the power supply. The junction of resistors 50 and 51 is connected to the screen 52 of thyratron 29. The output of difierentiator 34 is connected to the junction of resistors of 53 and 54-, the other end of resistor 53 going to the positive side of the power supply, and the other end of resistor 54 going to the negative side of the power supply.

Operation A sawtooth voltage shown at 101 in FIG. 3 is applied to terminal 11. At time t the voltage applied through voltage dividers comprising resistors 14 and 16 and resistors 17 and 18 and through D.C. amplifiers 26 and 28 to the control grids of thyratrons 29 and 31 will be a steady D.C. depending upon the settings of contacts 21, 23, 24 and 27. At this point of time the voltage as shown at 101 will begin to rise or become more positive linearly with time. At a time t the voltage applied to thyratron 29 will have reached the firing potential and thyratron 29 will fire. Applied to amplifier 32 this will result in steep wave front as shown at 1112 in FIG. 3b of wave-form B. At time t the voltage applied through voltage divider 14 and 16 and DC. amplifier 26 to thyra tron 31 will reach igniting potential and thyratron 31 will fire. The voltage at the output of thyratron 31 is shown by wave-form C of FIG. 3. At the point of firing, this will be a negative going front shown at 103. This voltage at 103 is applied to the screen grid of thyratron 29, which extinguishes thyratron 29. At this point the output of thyratron 29 will rise sharply as shown by waveform B at 104. The output Waveform will then be a complete rectangular square wave. At time t sawtooth wave-form A will fall as shown at 1%, which coupled through diiierentiator 34, will result in a negative going pulse shown at D of FIG. 3. This pulse is applied to screen grid 55 of thyratron 31. Thyratron 31 is extin guished at this point to await the next cycle of sawtooth A. it is to be noted at this point that resistors 19 and 22 have variable sliders Z1 and 23 which in effect change the resistance of resistors 19 and 22. These controls are ganged together and operate in opposite directions, i.e. when moveable tap 21 is being moved in an upward direction moveable tap 23 as the same time is moving in a downward direction. it will be appreciated that the voltage applied across voltage divider i4- and 16 and voltage dividers 17 and 18 will vary with the sliding of contacts 21 and 23. Thus when contact Zll is all the way to the top and contact 23 is all the way to the bottom a more positive potential will be applied at the top of resistors 14 and 17, and a more positive potential will be applied at the bottom of resistors of 16 and 18, giving a more positive shift to the overall available voltage. This will raise the potentials on the thyratrons to vary the time t Conversely, when contact 211. is at'the bottom of resistor 19 and contact 23 is at the top of resistor 22 both voltages across the voltage dividers go in a negative direction which again will vary the time t in this case to the right since it will take a longer time for sawtooth Wave-form A to overcome this bias. It is also pointed out that wipers 27 and 24 on resistors 17 and 16, respectively, are ganged together and also move in opposite directions, i.e. wiper 27 is moving up while wiper 24 is moving down. The difierence of the two D.C. operating potentials applied to thyratrons 29 and 31' will be varied by moving these controls. Thus, when Wiper 24 is at the top of resistor 16 and wiper 27 is at the bottom of resistor 17 there is a minimum of potential difi erence between the two thyratron grids and thyratron 31 will then fire closer tothyratron 29. The width of the square wave will be shortened in this case. Conversely, when the two wipers 27 and 24- are at their outer extremities, i.e. at the top of resistor 17 and the bottom of resistor 16, respectively, the voltage difference applied to the grids of the thyratrons will be the greatest, and the output waveform shown at B of FIG. 3 will be increased in width.

Referring now to FIG. 2, thyratron 29 is held below its firing potential by voltage divider 38 and 39, i.e. the voltage on cathode 41 is held at a much higher potential than grid as prior to the application of sawtooth A. As is well known in the art, when sawtooth A reaches the firing potential of thyratron 29 at time t thyratron 2.9 will fire and grid 36 will lose control of the tube. At this time the plate and screen potentials must drop below the extinguishing point, as determined by the particular tube characteristics in order to extinguish the tube. Screen 52 is applied to a voltage divider resistances b and Sll connected in series between plate 48 and the negative power supply terminal. At time t grid 4-3 of thyratron 31 has reached the same potential that grid 36 or" thyratron 29 had reached at time t The cathode 48 of thyratron 31 is returned to an identical voltage divider as cathode 41 of thyratron 29. Thus, at time t thyratron .31 will fire and again the control grid 43 will lose control of the tube. At this time plate 57 conducts current through resistor 49 dropping the plate voltage and decreasing, the voltage drop across resistor 51. This in turn will drop the potential applied to screen 52 of thyratron 29 below the extinguishing point and thyratron 29 will extinguish. At time I sawtooth A drops sharply as shown at 1% of waveform B. This drop is taken at the output of differentiator 34 as a sharp negative pulse. This negative pulse (waveform D) is applied to screen grid 58 and is of sufficient amplitude to extinguish thyratron 31.

Obviously many modifications and variations of the present invention are possible in light of the above teachings it is therefor to be understood that within the scope of the appended claims the invention may be practiced otherwise and as specificallyidescribed.

What is claimed is:

1. In a square-Wave voltage generator having a sawtooth-voltage input, first and second thyratrons, each thyratron having a cathode, a control grid, a screen grid, and an anode, means for applying a voltage to each of said cathodes, means for applying a voltage to each of said anodes, said cathode voltages being more negative than said anode voltages, a direct-current voltage source having first and second voltage outputs, the voltage at said first output being more positive than the voltage at said second output, means for coupling said control grid of said first thyratron to said first voltage output, means for coupling said control grid of said second thyratron to said second voltage output, input means for coupling said sawtooth voltage to each of said control grids, means coupled to said input means and to said screen grid of said second thyratron for differentiating said sawtooth voltage, and means for applying a voltage to said screen grid of said first thyratron, said voltage becoming more negative whenever said second thyratron conducts.

2. In apparatus for producing a square-wave voltage and having a sawtooth voltage input, first and second gaseous discharge tubes, each of said tubes having an anode, a screen grid, a control grid, and a cathode, first power supply means coupled to said cathodes for supplying voltage to each of said cathodes, second power supply means coupled to said anodes for supplying voltage to each of said anodes, said cathode voltages being more negative than said anode voltages, means coupled to said control grid of said first tube for biasing said control grid with a first direct-current voltage, means coupled to said control grid of said second tube for biasing said grid of said second tube with a second directcurrent voltage more negative than said first direct current voltage, input means for coupling said sawtooth voltage to both of said control grids, means coupled between said input means and said screen grid of said second tube for difierentiating said sawtooth voltage, and means coupled between said anode of said second tube and said screen grid of said first tube for supplying a voltage to'said screen grid of said first tube.

3. In a square-wave-voltage generator having a sawtooth voltage input, first and second gas tetrodes, said etrodes each having a cathode, a control grid, a screen grid and an anode, means for applying a voltage to each of said anodes, means for applying a voltage to each of said cathodes, said anode voltages being more positive than said cathode voltages, first variable voltage means for applying a bias voltage to said control grid of said first tetrode, a second variable voltage means for applying a voltage to said control grid of said second tetrode, input means for coupling said sawtooth voltage to each of said control grids, a differentiator connected between said input means and said screen grid of said second tetrode for diflferentiating said sawtooth voltage, and means for applying a negative-going voltage to said screen grid of said first tetrode whenever said second tetrode conducts.

4. In apparatus employing a positive-going sawtooth voltage for deriving a square-wave voltage, first and second thyratrons, each of said thyratrons having a cathode, a control grid, a screen grid and an anode, means for applying a voltage to each of said cathodes, means for applying a voltage to each of said anodes, said anode voltages being more positive than said cathode voltages, a direct-current voltage supply having first and second output voltages, said second output being more negative than said first output voltage, means for coupling said first output voltage to said control grid of said first thyratron, means for coupling said second output volta e to said control grid of said second thyratron, said output voltages being below the respective igniting potentials of said thyratrons, input means for coupling said sawtooth voltage to each of said control grids for igniting said thyratrons in timed relationship, means coupled between said anode of said second thyratron and said screen grid of said first thyratron for imposing a negative-going voltage on said screen grid of said first thyratron when said second thyratron ignites, and means coupled between said input means and said screen grid of said second thyratron for differentiating said sawtooth voltage.

References Cited in the file of this patent UNITED STATES PATENTS Sonnentag Mar. 25, 1941 Naslund Feb. 2, 1954 Leighton Mar. 16, 1954 

